The invention concerns a device for projection copying of masks onto a workpiece, particularly onto a semiconductor substrate, for the manufacturing of integrated circuits, whereby the patterns for the masks are copied once or several times on a light-sensitive layer of the workpiece by way of a projection lens, and the mask and workpiece are oriented to each other in a relative way such that the orientation pattern of the mask and the adjusting mark of the workpiece are thereby brought into a pre-determined spatial arrangement, so that the relative position of a sensor as well as of the orientation pattern of the mask and at least one reference mark for the workpiece on the base table are determined and then the adjusting mark of the workpiece is copied onto the sensor.
The simplest way of orienting the mask and the workpiece opposite each other is basically to align a mark on a mask with a mark on the workpiece by way of a projection lens. Due to the lacquer layers covering the workpiece necessary for the manufacturing of integrated circuits, there is, however, sometimes interference which hinders a reliable evaluation of the precision of the copying of both marks to one another. In such cases one must use procedures described at the outset which are relatively time-consuming and are not used for each single part of the workpiece but optimally only once for a step-wise exposure of an entire workpiece, that is for the so-called global adjustment.
Such a process is known from the European patent application No. 0045113, in which a mark aligned with a sensor is projected onto a reference mark aligned on the base table, that is the adjusting mark of the workpiece, by means of an accessory lens parallel to the projection lens. The same parallel lens is used to check the precision of this copying. Since the accessory lens allows a broad-band exposure in contrast to the projection lens, there are here no more interference phenomena. The imprecise knowledge of the opposite arrangement of accessory lens and projection lens is, however, a source of error.